My wife has a 1994 Plymouth Voyager (3.3L) and the heat barely warms up in this van. It's starting to get cold out and she is a heat monger.

Her fluid was low and she added some more anti-freeze which helped a tiny bit she says. But still very bad heat.

I have read many forums and such about this and so I checked the in and out pipes attached to the firewall are both hot and about the same temp. This tells me that there is good flow in the heater core. The engine seems to get plenty warm. The gauge on the dash is always mid way between cold and hot when running. I tore the dash board apart as much as i could and got the environmental control unit out. I checked the cable that controls the door in the heater section and as I move it from cold to hot, I can hear the door thunking to it's stop at each end of the motion. I disconnected it and confirmed that it is going at it's full range of motion when moving the arm on the controls. There is a definite change in temperature when moving the door back and forth, but it still isn't putting out hot air.

I can't tear the entire dashboard apart just to get into the box. It looks like you have to do some serious deconstruction just to get to the core, much less open it up and fix it, assuming there is even a problem inside of it.

I haven't changed the thermostat on the engine cause it seems like it must be doing it's job because the temp stays steady in the middle of the gauge.

Can anyone give me some more ideas? Short of trying to find some external heater for the van?

Thanks!!
Andrew

 

Well, you've checked the most obvious issues and they sound OK. The one thing I've run into is that if any air enters the system, it can be a real pita to "burp" the heater core. The fact that both heater hoses are hot isn't a sure sign that it is flowing well. Sometimes it takes many cooling and heating cycles for all of the air to get out. Another possibiblity is that the heater core is partially plugged. If all else fails, I would flush the cooling system with the strongest radiator flush you can find.

 

Thanks. I appreciate you taking the time. I don't think it's air because it's been this way for as long as we have had this van and that's almost been a year now. The people that had it before us had it for a couple years and said the heat has always been weak. It's more likely that's is jammed up.

Doing a flush has been recommended on several occasions. How would I go about doing that? I am not a mechanic so as far as I know, a flush is just drain and refill. What is involved? Is there special equipment or precautions to take?

Thanks again!!

 

put a higher temp thermostat thats your problem

 

I would go to Walmart or Autozone and buy the strongest radiator flush such as heavy duty Prestone. The instructions are self explanatory and no special equipment is needed. If money is an issue, you can collect the existing coolant and save it for re-installtion after flushing it.

 

It isn't your thermostat.... I had a 94 with the same problem. The damper on the box is not openeing or closing completely Part of the system is vacuum controlled and part is manual cable. From the driver side floor you can access the bottom pivot point of the damper. (Got this from a dodge tech in Upstate NY)
What you need to do is drill a small hole into the bottom of this (like 1/32) and spray lubricant into it and work the cable to get the damper moving. I ended up having to push on the top of the damper with a long rod through the heater contol opening (heat controlls pulled out of course), and then pull on the cable, spraying lube every so often. Finall freed it up enough to get good heat in side. Unfortunately my cable stretched a tiny bit, so during the summer I would have to manually close the heat door by pushing the cable in a little bit extra. (small price to pay for heat at 20 below).
The tech told me that condensation can get down there and oxidases so the damper won't move completely. Good luck....took me a couple of hours, but had heat for the next couple of winters.